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Solar System

The Solar System, drawn to scale, but not at the correct relative distances.
Credit:Wikimedia

The Solar System contains the Sun, eight planets with their moons, and lots of other smaller objects such as dwarf planets, asteroids and other Near Earth Objects (NEOs), and comets. The distances between planets in the Solar System are huge so we use a unit of measurement based on the average distance from Earth to the Sun, called an astronomical unit (AU).

The four planets closest to the Sun are called the inner or terrestrial planets and are typically small, warm, rocky worlds, that have few (or no) moons and no ring systems. They are: Mercury, Venus, Earth and Mars, the latter three have atmospheres and weather patterns.

The asteroid belt, containing some dwarf planets, then separates these inner planets, with the outer planets, which are much larger and cooler, and mainly made of gas. These outer planets all have a lot of moons and ring systems, although we can only see Saturn’s rings from Earth. Also known as gas giants, they are mainly made of gases and ices and together make up 99% of the mass that orbits the Sun. They are: Jupiter, Saturn, Uranus and Neptune.

Beyond this are many of the other dwarf planets of our Solar system, and icy comets.